The voltage of the neutral wire is 0 volts when measured relative to the earth wire. This fundamental characteristic makes the neutral wire a crucial part of an electrical circuit, providing a return path for current.
Understanding Mains Electricity Wires
In a typical mains electricity setup, especially in the UK as referenced by the BBC Bitesize guide, there are three primary wires, each serving a distinct purpose:
- Live Wire: This wire carries the alternating current (AC) at a high voltage, typically 230 V in the UK. It is the dangerous wire as it carries the full potential.
- Neutral Wire: This wire completes the circuit by providing a return path for the current from the appliance back to the electricity supply. It is intentionally kept at or near earth potential.
- Earth Wire: This is a safety wire connected to the metal casing of appliances. In the event of a fault (e.g., if the live wire touches the casing), it provides a low-resistance path for current to flow safely to the ground, triggering protective devices like circuit breakers or fuses.
Voltage Relationships Between Wires
Voltage is always a measurement of potential difference between two points. The provided BBC Bitesize reference clearly outlines the voltage relationships between these wires:
| Wires | Voltage Between Them (V) |
|---|---|
| Live and Neutral | 230 |
| Live and Earth | 230 |
| Neutral and Earth | 0 |
As shown in the table from the BBC Bitesize guide on Live, Neutral, and Earth Wires, the voltage between the neutral wire and the earth wire is 0 volts. This is why the neutral wire is considered to be at earth potential, making it safe to touch under normal operating conditions, unlike the live wire.
Practical Implications
The neutral wire's 0-volt potential relative to earth is critical for:
- Circuit Completion: It provides the necessary low-potential return path for current to flow from the high-potential live wire through an appliance.
- Safety: By being at earth potential, it minimises the risk of electric shock if touched, although it is still always advisable to treat all wires in a circuit with caution.
- System Stability: Maintaining the neutral wire at earth potential helps in stabilising the electrical system and providing a common reference point for voltage measurements.
In summary, while the live wire carries the full mains voltage, the neutral wire acts as the return path and is maintained at a negligible voltage (0V) relative to the earth, ensuring the safe and efficient operation of electrical systems.
